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Honors Chemistry Unit 5 – The Mole. Lesson 6 – Molecular Formulas Book Section: 7-4 Objective: SWBAT determine molecular formulas of compounds using mass data. Do Now: Prepare for Quiz 5-5. Molecular Formulas. The true formula for a chemical substance is its molecular formula.
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Honors ChemistryUnit 5 – The Mole Lesson 6 – Molecular Formulas Book Section: 7-4 Objective: SWBAT determine molecular formulas of compounds using mass data. Do Now: Prepare for Quiz 5-5
Molecular Formulas • The true formula for a chemical substance is its molecular formula. • It is a whole-number multiple of the empirical formula. • The molecular formula of a compound can be determined from two pieces of information: • The empirical formula of the compound • The molar mass of the compound.
Determining Molecular Formulas • Step 1: Find the empirical formula of the compound. • Step 2: Find the molar mass of the empirical formula. • Step 3: Divide the molar mass of the compound by the molar mass of the empirical formula to get a whole number. • Step 4: Multiply the subscripts of the empirical formula by this whole number to get the molecular formula.
Determining Molecular Formulas • Determine the molecular formula for an oxide that contains 21.03 g of nitrogen and 47.97 g of oxygen and has a molar mass of 92 g/mol. • Step 1: Find the empirical formula of the compound. • Step 2: Find the molar mass of the empirical formula. • Step 3: Divide the molar mass of the compound by the molar mass of the empirical formula to get a whole number. • Step 4: Multiply the subscripts of the empirical formula by this whole number to get the molecular formula.
Homework: #34-37 • This week: • Friday: Selective Precipitation of Cations Lab Day 1, Quiz 5-6 • Next week: • Monday: Selective Precipitation of Cations Lab Day 2, Quiz 5-7 • Tuesday: Selective Precipitation of Cations Lab Day 3 • Review: Monday, November 29 • The Mole Exam: November 30